This invention refers to a system of elements of plastic material intended for the composition, by means of frictional insertion, of static or dynamic constructions having a game or didactic purpose.
There are known several systems of elements of plastic material which can be mutually connected by means of frictional insertion, and which enable composing static constructions, to which some dynamic elements can also be applied. In most such systems each element is provided with at least one male coupling member and at least one female coupling member, and the composition is obtained by mutually inserting a male coupling member of an element into a female coupling member of another element. A first drawback resulting from this principle resides in that the male and female coupling members, since they pertain to the same elements, are unavoidably formed by the same material, whereby the efficiency of their frictional insertion only depends on the accuracy of the dimensions of the parts and on the own elasticity of the material. This material, since it should form the entire element, cannot be chosen with complete freedom, due to technical requirements, to reasons depending on a pleasant use and to economic restrictions. Therefrom there can result a somewhat weak coupling which, in particular, can be jeopardized by permanent deformations of elements remained connected for a long time, due to the so-called "cold flux" to which several plastic materials are subjected. This phenomenon is aggravated by the male coupling members generally having a very reduced extent.
A remedy to this drawback has been found, according to the Italian Patent No. 1.147.731, by means of elements in which the male coupling members are applied to the element body and, therefore, can be embodied in a material different from that forming the body of the elements and the female coupling members. However, it is evident the economical burden resulting both from the manufacture of the elements in several parts, and from the need of mounting together said parts.
Moreover, it is a common feature of most known systems that the symmetry of the coupling members is generally of order four, whereby the elements can be mutually connected only according to a number of positions which mutually differ by displacements of 90.degree.. In those cases in which the arrangement according to a different angle, for example of 45.degree., should be allowed, this cannot be obtained by means of the normal elements of the system, and special elements intended for this purpose should be provided, however this is contrary both to the manufacture economy and the systematicity of the composition.